1. Field of the Invention
The present invention relates to a passenger protection apparatus which is capable of estimating the position of a passenger in a passenger's compartment of a vehicle thereby to control an air bag in an optimal manner.
2. Description of the Related Art
Conventional passenger detection or protection apparatuses are described for example in Japanese Patent Application Laid-Open No. 6-206514, Japanese Patent Application Laid-Open No. 10-44921, etc. Hereinafter, Japanese Patent Application Laid-Open No. 6-206514 and Japanese Patent Application Laid-Open No. 10-44921 will be described in detail.
As shown in FIG. 16, a passenger detection or protection apparatus disclosed in Japanese Patent Application Laid-Open No. 6-206514 includes a displacement sensor 60, which is mounted on a dashboard 24 for detecting the distance of a passenger or occupant 34 on a seat in a passenger's compartment from the storage position of an air bag 26, and an infrared sensor 70, which is mounted on the ceiling of the vehicle over the head of the passenger and has a plurality of fields of view VF1–VF8.
These sensors 60, 70 supply output signals corresponding to the distance of the passenger 34 to the stored air bag 26 to a control device 50, so that when at least one of these signals from the two sensors 60, 70 indicates that the passenger 34 is at a prescribed distance or more apart from the air bag storage position, the control device 50 sends an enable signal to a passenger restraint system 20 to make the air bag 26 into an operating state in which it is expandable. On the contrary, when the distances detected by both of these sensors 60, 70 are less than the prescribed distance, the control device 50 makes the air bag 26 into an inoperable state. That is, when the passenger 34 is close to the dashboard 24, the air bag 26 is controlled to prevent its expansion. Here, note that the level of the expansion of the air bag 26 may be controlled in accordance with the distance of the passenger 34 to the air bag, thus making it possible to control the passenger restraint system 20 in an appropriate manner.
In addition, in a passenger detection or protection apparatus disclosed in Japanese Patent Application Laid-Open No. 10-44921, as shown in FIG. 17, an air bag 26 is accommodated in an air bag accommodation part 3 of a dashboard 24 so that it is caused to inflate or expand like a balloon at the time of sudden deceleration, thereby protecting a passenger on a seat. In FIG. 17, a warning area 4 represents an area in which a high impact might be brought to the passenger upon expansion of the air bag 26. A range sensor (infrared sensor) 70 monitors whether there exists any person or object in the warning area 4. When anyone or anything continuously stays in the warning area 4 for longer than a predetermined period of time, a warning is output, or a related air bag system is controlled to prevent the air bag 26 from being opened or expanded even in case of sudden deceleration.
However, with the passenger protection apparatus of Japanese Patent Application Laid-Open No. 6-206514 as shown in FIG. 16, the specific distance of the passenger from the air bag storage position or expansion surface is detected or recognized so that the air bag 26 is intended to be controlled in accordance with the distance and the moving speed of the head of the passenger 34 (i.e., in actuality, the crash or collision position of the air bag 26 with the passenger 34 calculated or estimated from the distance and the moving speed of the passenger's head). Therefore, there might be a possibility that the sensors are of complicated constructions, and the amount of arithmetic calculations increases.
Moreover, although it is necessary to control the air bag 26 in accordance with the position of crash or collision between the air bag and the passenger's head, it is practically difficult to measure the moving speed of the passenger's head after the collision. In addition, the air bag control has not a one-to-one relation to the collision position of the air bag with the passenger's head, but there exists a certain extent of overlap therebetween, so there is a possibility that the exact collision position of the air bag with the passenger's head cannot be instantaneously determined or distinguished.
Furthermore, with the passenger protection apparatus as shown in Japanese Patent Application Laid-Open No. 10-44921, only a dangerous area is monitored so as to distinguish the passenger's head from his or her hands or other objects based on their staying time in which they continuously stay in the dangerous area. As a result, it might be unable to instantaneously determine or distinguish, upon collision, the incoming or entering of passenger's hands, a newspaper or the like into the dangerous area.